This invention relates to ozone generators and in particular to ozone generators for producing small quantities of ozone from air. The ozone generators can be used to reduce or eliminate odours in, for example, public washrooms although other uses are contemplated such as in kitchens, coolers, etc. In the ozone generators disclosed herein the initiation of a corona discharge and the resulting ion wind from the corona are sufficient to displace air through the apparatus for the continuous production of both ions and ozone.
The production of ozone in a direct current corona has been investigated by numerous researchers. The basic mechanisms of the direct current corona have been documented by L. B. Loeb in two texts, viz. "Basic Processes of Gaseous Electronics", University of California Press, Berkeley and Los Angeles, 1955 (Second Edition 1961) and "Electrical Coronas--Their Basic Physical Mechanisms", University of California Press, Berkeley and Los Angeles, 1965. However, the quantitative evaluation of ozone production in coronas is not discussed in either of these references. The ozone production from pointed electrodes and wire electrodes have been reported in the literature (Goldman M., Lecuiller M. and Palierne M., Gaseous Discharges III, Pergamon Press, 1982 p 329; Peyrous R. and Lacase C, Ozone Science and Engineering 8, pp 107-128, 1986). In much of this work there is general disagreement about the efficiency of ozone production in positive or negative coronas, and the role of electrode materials in improving ozone production by catalytic processes. The production of ozone in large quantities by corona discharges using a primary and secondary corona process in confined tubulation with forced air flow, has been described in U.S. Pat. No. 4,062,748. This apparatus requires the forced circulation of air or oxygen through tubular arrays, to ozone outputs at the level of grams per hour. Canadian Patent No. 935,784 of Corbeil, issued Oct. 23, 1973 describes a gas treatment apparatus in which ozone is produced by a direct current corona between a sharp point and a section of spherical gauze as the counter electrode. The device is enclosed in a tube of insulating material and disperses ozone with the aid of the associated ion wind. No measurements or estimates of the amount of ozone produced are included in the patent.
From the work of Loeb, it is clear that in the silent DC corona there can be marked differences in the effective temperature of the corona, depending on the local current density in the discharge. As the corona degenerates to an arc, this temperature further increases. It is known that in this arc mode, the production of ozone is small, as ozone produced by dissociation of oxygen by ion impact, is quickly reverted to oxygen at the elevated temperature of the arc. Even in silent corona discharges it is important to control the local temperature in the discharge, so that ozone is not rapidly converted to oxygen after initial formation. As a result, the discharge from sharp points is to be avoided if the ozone is to be produced efficiently in low current corona discharges.
U.S. Pat. No. 4,507,266 of Satoh, et al, issued Mar. 26, 1985, discloses an electrode structure having a plurality of edges. Glow discharge is generated between edge portions 4a, 4b of the projected portions 4 on the surface of the cathode 2 and the anode 3.
Canadian patent No. 920,088 of Beitzel, issued Jan. 30, 1973, discloses a tubular electrode structure for an ozone generator including a dielectric tube 12 with an electrode 14 on the inner surface of the tube and an electrode 16 on the outer surface of the tube.
Many types of ozone generators are known in the art. For example, ozone generators having plate type electrodes are disclosed in Canadian patent No. 920,979 of Schaefer, issued Feb. 13, 1973 and in Canadian Patent No. 1,090,293 of Pavel, issued Nov. 25, 1980.